Consider the potentiometer circuit shown in the figure below. The potentiometer wire is 600 cm long. At what distance from point A should the jockey be placed to get zero deflection in the galvanometer?
320 cm
For zero deflection of the galvanometer, no current will flow in the secondary circuit.
Current through the potentiometer wire, I=Er+15r=E16r
Suppose the distance from end A where the jockey is placed be x cm. The drop across this length of potentiometer wire will be E2.
E2=I×x600×15r⇒E2=E16r×x600×15r∴x=320 cm